A power semiconductor device, such as a power module, operates with a large current and a high voltage. For this reason, it is essential to efficiently discharge heat, which is generated by the operation of the power semiconductor device, to the outside of the power semiconductor device. Accordingly, in a power semiconductor device, a wiring pattern is formed on a metal plate that acts as a heat sink, while an insulation layer is interposed between the wiring pattern and the metal plate. A power semiconductor element is provided on the wiring pattern. The power semiconductor element is sealed with resin.
One of such power semiconductor devices is formed with: a metal plate acting as a heat sink; a wiring pattern formed on the metal plate, having a ceramic plate interposed between the wiring pattern and the metal plate as an insulation layer; external lead terminals joined to the wiring pattern, which rise from a surface on which power semiconductor elements are mounted; metal wires connecting the external lead terminals to the power semiconductor elements; an external casing formed of thermoplastic resin, which is bonded to the metal plate; silicon gel filled in a concave portion formed with the external casing and a substrate on which the power semiconductor elements are mounted; and heat-hardening resin filled above the silicon gel (see, e.g., Patent Document 1)
However, in manufacturing of this conventional power semiconductor device, there are: a process of bonding the external casing, which is formed of thermoplastic resin, to the metal plate; a process of filling and curing the silicon gel; and a process of injecting and curing the heat-hardening resin. Thus, there are a large number of manufacturing processes, causing a prolonged manufacturing time. Accordingly, there is a problem of low productivity.
A power semiconductor device which solves this problem and which is excellent in productivity is a power semiconductor device in which: a lead frame is provided on a metal plate while an insulation layer is interposed between the lead frame and the metal plate; and power semiconductor elements are mounted on the lead frame and sealed with transfer molding resin (see, e.g., Patent Document 2).
[Patent Document 1] Japanese Laid-Open Patent Publication No. H08-316357 (Page 3, FIG. 1)
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2001-196495 (Page 3, FIG. 1)